The data only consider carbon dioxide emissions from the burning of fossil fuels and cement manufacture, but not emissions from land use, land-use change and forestry.[n 2] Over the last 150 years, estimated cumulative emissions from land use and land-use change represent approximately one-third of total cumulative anthropogenic CO2 emissions.[7] Emissions from international shipping or bunker fuels are also not included in national figures,[8] which can make a large difference for small countries with important ports.
In 2023, global GHG emissions reached 53.0 GtCO2eq (without Land Use, land Use Change and Forestry). The 2023 data represent the highest level recorded and experienced an increase of 1.9% or 994 MtCO2eq compared to the levels in 2022. The majority of GHG emissions consisted of fossil CO2 accounting for 73.7% of total emissions.[4]
China, the United States, India, the EU27, Russia and Brazil were the world’s largest GHG emitters in 2023. Together they account for 49.8% of global population, 63.2% of global gross domestic product, 64.2% of global fossil fuel consumption and 62.7% of global GHG emissions. Among these top emitters, in 2023 China, India, Russia and Brazil increased their emissions compared to 2022, with India having the largest increase in relative terms (+ 6.1%) and China the largest absolute increase by 784 MtCO2eq.[4]
CO2 emissions from the top 10 countries with the highest emissions accounted for almost two thirds of the global total. Since 2006, China has been emitting more CO2 than any other country.[9][10][11] However, the main disadvantage of measuring total national emissions is that it does not take population size into account. China has the largest CO2 emissions in the world, but also the second largest population. Some argue that for a fair comparison, emissions should be analyzed in terms of the amount of CO2 per capita.[12] Their main argument is illustrated by CO2 per capita emissions in 2023, China's levels (9.24) are almost two thirds those of the United States (13.83) and less than a sixth of those of Palau (62.59 – the country with the highest emissions of CO2 per capita).[4][13]
Measures of territorial-based emissions, also known as production-based emissions, do not account for emissions embedded in global trade, where emissions may be imported or exported in the form of traded goods, as it only reports emissions emitted within geographical boundaries. Accordingly, a proportion of the CO2 produced and reported in Asia and Africa is for the production of goods consumed in Europe and North America.[14]
Greenhouse gases (GHG) – primarily carbon dioxide but also others, including methane and chlorofluorocarbons – trap heat in the atmosphere, leading to global warming. Higher temperatures then act on the climate, with varying effects. For example, dry regions might become drier while, at the poles, the ice caps are melting, causing higher sea levels. In 2016, the global average temperature was already 1.1°C above pre-industrial levels.[15]
^Carbon dioxide (CO2) is a colourless, odourless and non-poisonous gas formed by combustion of carbon and in the respiration of living organisms and is considered a greenhouse gas. Emissions means the release of greenhouse gases and/or their precursors into the atmosphere over a specified area and period of time. Carbon dioxide emissions or CO2 emissions are emissions stemming from the burning of fossil fuels and the manufacture of cement; they include carbon dioxide produced during consumption of solid, liquid, and gas fuels as well as gas flaring
^Global Carbon Project (2022)[5] The rate of build-up of carbon dioxide (CO2) in the atmosphere can be reduced by taking advantage of the fact that atmospheric CO2 can accumulate as carbon in vegetation and soils in terrestrial ecosystems. Under the United Nations Framework Convention on Climate Change any process, activity or mechanism which removes a greenhouse gas (GHG) from the atmosphere is referred to as a "sink". Human activities impact terrestrial sinks, through land use, land-use change and forestry (LULUCF), consequently, the exchange of CO2 (carbon cycle) between the terrestrial biosphere and the atmosphere is altered.[6]
^Greenhouse gases (GHG) constitute a group of gases contributing to global warming and climate change.
The Kyoto Protocol, an environmental agreement adopted by many of the parties to the United Nations Framework Convention on Climate Change (UNFCCC) in 1997 to curb global warming, nowadays covers seven greenhouse gases:
the non-fluorinated gases:
carbon dioxide (CO2),
methane (CH4),
nitrous oxide (N2O),
the fluorinated gases:
hydrofluorocarbons (HFCs),
perfluorocarbons (PFCs),
sulphur hexafluoride (SF6),
nitrogen trifluoride (NF3).
Converting them to carbon dioxide (or CO2) equivalents makes it possible to compare them and to determine their individual and total contributions to global warming.
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